Improve diagnostics and add code fixes for top-level await

[Ron Buckton (rbuckton)]

This improves the diagnostic messages for top-level await and adds several code-fixes to improve the experience.

In addition, this fixes a small bug in our textChanges algorithm to ensure we correctly add new-lines when inserting nodes at the top of a class body/object literal (and elide trailing commas in an object literal when they aren't needed.

Fixes #36036
Fixes #36171

[Daniel Rosenwasser (DanielRosenwasser)]

Looks like there's a merge conflict.

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[TypeScript Bot (typescript-bot)]

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the tarball bundle task on this PR at 80b065f. You can monitor the build here. It should now contribute to this PR's status checks.

[Daniel Rosenwasser (DanielRosenwasser)]

The message improvements look good.

I would suggest always keeping the trailing comma to be honest - but I happen to be especially prone to adding new fields after members that lack a comma.

[Ron Buckton (rbuckton)]

Daniel Rosenwasser (@DanielRosenwasser): Trailing comma is illegal in JSON, so if we ever have a codefix that affects package.json, it would make that file invalid. I'd rather trim the trailing comma to be safe.

[Daniel Rosenwasser (DanielRosenwasser)]

Would it be too much trouble to have the codefix check if it's in ES3 or working under JSON?

[Daniel Rosenwasser (DanielRosenwasser)]

or have the printer "do the right thing" under either mode?

[Ron Buckton (rbuckton)]

I've updated it so that it only elides the trailing comma when the source file is a .json file (since there's no way to tell whether it's a normal .json or a non-standard .json like our tsconfig files).